Improvement of regional seismic hazard assessment considering active faults
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Τσιπιανίτης, Αλέξανδρος
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Abstract
Seismic hazard assessment is a required procedure to assist effective designing of structures located in seismically active regions. Traditionally, in a seismically active region as Greece, the seismic hazard evaluation was based primarily on the historical seismicity, and to lesser extent based on the consideration of the geological information. The importance of the geological information in seismic hazard assessment is significant, for the reason that earthquakes occur on faults. This approach also covers areas with few instrumental recordings. Mapping, analyzing and modeling are needed for faults investigation. In the present dissertation, we examined the seismic hazard for the cities of Patras, Aigion and Korinthos, considering the seismically active faults. The active faults considered in this investigation consists of 148 active faults, for which a minimum amount of information was available (i.e. length, maximum magnitude, slip rate, etc.). For some critical parameters, e.g. slip rate, if an estimate could not be found in the literature it was calculated based on empirical laws. Specifically, the slip rate for each fault was resulted from the division of total displacement with the stratigraphic age. Two different approaches (historical seismicity, length of faults) were followed for the estimation of total displacement for each fault. A distribution of slip rates was made because uncertainties are considered. The resulted slip rates were converted into seismic activity. Thus, we were able to construct a complete database for our research. Epistemic uncertainties were accounted at both seismic source models as well as at the ground motion via a logic tree framework resulted in two different calculation procedures (including or not the b value uncertainty). The seismic hazard model was implemented following the OpenQuake open standards – NRML, and the seismic hazard computation was performed for the region of interest. The seismic hazard was quantified in terms of seismic hazard maps, hazard curves and uniform hazard spectra for the region of interest. Different intensity measure types were considered, Peak Ground Acceleration, Spectral Acceleration at two fundamental periods 0.1 and 1.0 sec. Finally, the results of this thesis were compared with the Greek Seismic Code and other seismic hazard estimations for the investigation region.
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Seismic hazards, Gulf of Corinth, Engineering, Seismology, Openquake